Vertical drying machine



HISAYOSHI KUBODERA 3,510,960

VERTICAL DRYING MACHINE May 12, 1970 2 Sheets-Sheet 1 Filed June 6, 1968FIG.

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VERTICAL DRYING MACHINE 2 Sheets-Sheet 2- Filed June 6, 1968 FIG. 2

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BY mum United States Patent Office 3,510,960 VERTICAL DRYING MACHINEHisayoshi Kubodera, 19-10 2-chome, Shinbashi, Minato-ku, Tokyo-to, JapanFiled June 6, 1968, Ser. No. 735,087 Claims priority, application Japan,June 10, 1967, 42/36 66 Int. Cl. F26b 13/00 US. Cl. 34-155 9 ClaimsABSTRACT OF THE DISCLOSURE A vertical drying chamber containing aheating device is vertically passed through by a strip material to bedried. The strip runs along an inverted U-shaped path in the chamberover a strip guide roller located at. the top of the drying chamber.Below the guide roller and above the top of the drying chamber, thereare provided transverse air curtain creating nozzles which direct aironto the surface of the runs or spans of the strip and prevent heattransfer and leak of fluid from the chamber to the rollers.

BACKGROUND OF THE INVENTION This invention relates to drying machinesand, more particularly, to a drying machine of the vertical type havinga drying chamber or tower through which a material to be dried ispassed.

In a typical example of the drying machine of the above type, thevertical drying chamber has at the upper portion thereof a horizontalguide roller, and a strip material to be dried is continuously passedthrough the drying chamber in an inverted U-shaped path with theuppermost part of the U-shaped material passing over the guide roller.The material to be dried may, for example, be one wvhich has been passedthrough a bath of a treating medium dissolved in a solvent.

Such drying machines of the vertical type have various advantages overthose of the horizontal type. However, the machines of the vertical typeare accompanied by some serious problems which give rise to difficultyin attaining satisfactory operation.

-In the vertical drying machine, the upper part of the drying chambertends to be excessively heated by the heat generated in the chamber, anda heated mixture of air and solvent in the chamber tend to leak throughthe upper part of the drying chamber. These tendencies usually result inadhesion or sticking onto the guide roller of the treating mediumapplied on the strip material, and this often leads to damage to thematerial being treated.

Thus, the feed speed of the material to be subjected to drying operationis usually limited in the conventional machines by the sticking of thematerial to the guide roller at high speeds due to temperature rise inthe guide roller.

Another problem in the maintenance of the machine is that, when the capcovering the guide roller is removed, leakage of the air and solventoccurs in great quantity from the drying chamber.

A simple method of cooling the guide roller from the inside has beenresorted to for prevention of adhesion or sticking. However, thisexpedient is not satisfactory because the solvent vapor and moisture inthe air tend to condensate on the surface of the guide roller.Furthermore, when the temperature of the material surface is higher thanthat of the guide roller, the treating medium on the material tends tobe transferred onto the surface of the guide roller with resultantdamage to the material being dried.

3,510,960 Patented May 12, 1970 SUMMARY OF THE INVENTION Accordingly, amain object of this invention is to provide a novel drying machine ofthe vertical type which is free of the above mentioned disadvantages.

Another object of this invention is to provide a novel drying machinewherein heat transfer from inside the drying chamber to the guide rollerabove the chamber and leakage of air and solvent from the drying chambertop are prevented.

Briefly stated, in accordance with a preferred embodiment of thisinvention, there is provided at least two vertically spaced sets of aircurtain creating means which are located below the guide roller andabove the top end of the vertical drying chamber. Each of the aircurtain creating means includes air ejector nozzles so arranged that theupwardly and downwardly extending spans of the strip-like materialrunning along the inverted U- shaped path are passed between opposingnozzles which direct air toward both surfaces of each span to. createair curtains or air stream layers for preventing ascent or leakage ofthe hot air and solvent in the drying chamber along the spans of thematerial to the guide roller. The space between the upper and lower setsof air curtain creating means receives the air ejected from the nozzlesand serves to discharge the air to any desired place.

BRIEF DESCRIPTION OF THE DRAWING In the drawings:

FIG. 1 is a diagrammatic vertical section of an embodiment of thisinvention; and

FIG. 2 is an enlarged vertical section of a top assembly.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawing, thedrying machine comprises a vertical housing 10 defining a dryingchamber, which is divided by a vertical partition wall 11 into a pair ofsub-chambers 12 and 13 communicating with each other at their upperends. These subchambers 12 and 13 have therein heating means 14 whichare arranged along the length of the sub-chambers and allow the strip Sto be treated to pass therealong. The heating means 14 may be in theform of a series of pipes through which steam flows.

The sub-chamber 12 is provided with an inlet opening 15 for the strip Sat the lower end thereof, and the subchamber 13 is provided with anoutlet opening 16 for the strip S at the lower end thereof.

On the top of the housing 10, there is rigidly mounted a top assembly 20having a removable cap 21. The top assembly 20 carries a rotatableroller 22 over which the strip S passes.

The strip 6 to be treated is supplied from a supply source (not shown)into a bath B of an appropriate treating medium which may, for example,be a coating material dissolved in a solvent. The strip which has beencoated with the material of the bath B is fed through the inlet opening15 into the sub-chamber 12 to be heated or dried by the heating means 14and then passes over the roller 22 to be fed into the other sub-chamber13. The strip is additionally subjected to heating or drying treatmentwhen it passes through the sub-chamber 13, and is taken out from thechamber through the outlet opening 16.

The lowermost part of the subchamber 12 is communicatively connected toa cooling unit 30 through a conduit 31. The cooling unit 30 includestherein a cooling means 32 which may be a series of pipes through whichcooling medium flows. The unit 30 is provided with a condensatecollecting means 33.

The cooling unit 30 is communicatively connected through a conduit 35 toan air preheater unit 40 having therein heating means 41 which may, forexample, be a series of pipes through which steam flows. The airpreheater unit 40 is connected through a conduit 42 with the lowermostpart of the sub-chamber 13. One of the conduits 31, 35 and 42 may beprovided therein with a fan 34 for forced circulation.

The vertical type drying machine as described above is known per se andoperates as follows.

As the strip S, with the treating medium applied thereon in the bath B,is fed into the drying chamber 12 and 13, it is subjected to heatgenerated from the heating means 14 with the resultant evaporation ofthe solvent from the surfaces of the strip. This evaporation causes thestrip to be dried. The evaporated solvent in the drying chamber is drawnby the fan 34 through the conduit 31 into the cooling unit 30 and iscondensed on the cooling means 32, thus flowing down to the condensatecollecting means 33 to be taken out therefrom.

The fan 34 also draws heated air in the drying chamber. The air iscooled by the cooling means 32 and fed through the conduit 35 into theair preheater unit 40 to be preheated thereby. The preheated air fromthe unit 40 flows into the sub-chamber 13 and passes upwardly along thestrip being fed in counter-current flow relative to the latter to beagain drawn to the fan 34 through the sub-chamber 12. In the course offlowing along the strip in countercurrent flow thereto, the air promotesthe evaporation of the solvent on the surfaces of the strip passingthrough the drying chamber.

The novel features of this invention reside in the provision of meansincluding at least two sets of air curtain devices.

In accordance with the embodiment shown in the drawing, the top assemblyincludes a housing 50' in which are contained two sets of air-curtaindevices.

The first or upper set of air-curtain devices comprises a pair of nozzlemounting members 51a and 51b rigidly secured on the inner wall of thehousing 50 and a central nozzle mounting member 510 rigidly secured tothe housing 50. These mounting members 51a, 51b and 51c extend inparallel spaced apart relationship to each other and carry air ejectionnozzles.

The mounting members 51a and 51b rigidly carry air nozzles 52a and 52b,and the central mounting member 510 rigidly carries on both sides airnozzles 520. The opposing pairs of nozzles 52a, 52c and 52b, 52crespectively form gaps therebetween through which the upward anddownward spans of the strip pass. The pair of nozzles 52a and 520 are onthe same horizontal level and eject air streams toward each other ontothe adjacent surfaces of the running strip, thus forming a kind of aircurtain extending transversely to the running direction of the strip.The relation between the other pair of nozzles 52b and 520 are identicalwith that between nozzles 52a and 52c, the upwardly run traveling spanof the strip passing between the nozzles 52b and 520.

The second or lower set of air-curtain devices is identical with thefirst or upper set and therefore will not be explained in detail.

The upper set of air-curtain devices is disposed between horizontalplates 55 and 56 having openings for the spans of the strips, and thelower set of air-curtain devices is disposed between horizontal plates57 and 58.

Between the upper and lower sets of the air-curtain devices, there isformed an intermediate space 60 which is in communication with theinternal spaces of both the upper and lower sets of air-curtain devices.The space 60 is connected with an air discharge conduit 61 having acontrol valve 62.

A space 66 below the lower set of air-curtain devices is incommunication with the drying chamber through openings 63 allowing thepassage of the spans of the strip and also in communication with theinternal space of the lower set of air-curtain devices. The space 66 iscon- 4 nected With a discharge conduit 64 having a control valve 65.

In this type of the drying machine, it is desirable that the circulatingair in the machine be prevented from flowing out of the machine. Whenthe circulating air escapes, the drying efliciency of the machine andthe rate of recovery of the solvent will naturally be decreased. Theescape of the circulating air will also cause pollution of theatmosphere. In the vertical type drying machine, leakage of the internalfluid is most likely to occur in the upper part of the drying chamberbecause the pressure difference between the atmosphere and the internalair becomes the greatest at the uppermost part of the drying ghamber dueto the internal heat generated in the cham- This difficulty can beeliminated with the air curtain devices of this invention.

In the course of the drying operation, the hottest air in the dryingchambers 12 and 13 gathers in the uppermost part thereof. Such air may,if desired, be exhausted to the outside remote from the machine throughthe conduit or chimney 64, and the exhaust may be stopped by closing thevalve 65.

Under the closed condition of the control valve 65, the mixture of theair and solvent in the uppermost part of the drying chamber tends toascend through the lower set of the air curtain devices. However, mostof this mixture cannot pass through the air curtains or air streamlayers, whereas these curtains or layers permit the strip to freely passtherethrough.

A small part of the mixture of the air and solvent, however, fiows intothe space 60 with the injected air of the nozzles. This part of themixture is further resisted by the air curtains or air streams createdin the upper set of the air curtain devices and cannot ascendfurthermore. Thus, it will be noted that the hot mixture of air andsolvent can in no way fiow along the running strip into the internalspace directly below the removable cap 21. The small part of the mixturewhich flows into the space 60 may be exhausted through the conduit orchimney 61 to a place remote from the machine.

Since the space 60 is always filled with cool air which has just beenejected from the lower set of the air curtain devices and the cool airis exhausted to carry off the heat of the hot mixtures which passthrough the air curtains of the lower sets, almost no heat from thedrying cham* ber reaches the roller 22 of the top assembly. It will benoted that the maintenance of the roller 22 in a cool condition and theprevention of leakage of the mixture to the roller 22 make it possibleto prevent adhesion or sticking of the treating medium to the roller.

Because the pressure in the space surrounding the roller 22 ismaintained substantially the same as that in the drying chamber in theclosed condition of the cap 21, the ejection of air from the nozzles ofthe air curtain devices need not be very strong.

In the space surrounding the roller 22, there may be provided an airejection device 70 which directs cool air onto the surface of the strippassing through the space. When such a device 70 is additionallyprovided, the prevention of leakage of the mixture of air and solventfrom the drying chamber will be more effective because the air ejectedfrom the device 70 flows into the space 60 so as to further restrain theleakage of the mixture toward the roller 22. The rate of exhaust throughthe conduit or chimney '61 can be appropriately adjusted by the controlvalve 62. When the valve 62 is set to a position in which the amount ofair exhausted from the top assembly 20 is equal to that introduced intothe assembly, the optimum condition is obtained.

Such a condition can also be attained by connecting the conduit 61 tothe conduit 64 so as to form a closed circuit for the air. Thisprocedure is advantageous because the closed circuit of air flow shutsout outside dust and prevents clogging of the air-curtain nozzles andbecause the closed circuit makes it possible to cool the air exhaustedfrom the conduit 61 before it is again supplied to the conduit 64, forthe purpose of maintaining constant operating condition. On the otherhand, this procedure has the drawback of requiring removal of thesolvent intermixed with the exhaust air before the air is again returnedto the conduit 64.

Since the downward span of the strip coming from the roller 22 is in acooled condition and the upward run of the strip coming from the dryingchamber is in a hot condition, it is desirable that the air-curtaindevices associated with the downward traveling span eject heated air towarm the span and that those associated with the upward traveling spaneject cooled air to cool the run.

Furthermore, it is preferred that the lower set of the air-curtaindevices supplies appropriately heated air to prevent condensation of thesolvent in the drying chamber onto the air-curtain nozzles exposed tothe chamber and to prevent condensed solvent on the nozzles from beingsplashed onto the strip by the ejection force of the air.

In the embodiment shown, the air ejected from the lower set of aircurtain devices is supplied into the intermediate space 60. However, theair may be supplied into the lower space 62 so as to be exhaustedthrough the conduit 64.

It is preferred that the nozzles be located as close as possible to thesurfaces of the strip. However, it is important that the nozzles do notcontact the strip.

When it is necessary to remove the cap 21, the control valve 65 is fullyopened to direct the ejected air from the lower set of air curtaindevices into the chamber 63. This effectively prevents the mixtures inthe drying chamber from leaking in the upward direction.

Although this invention has been described with reference to aparticular embodiment, it should be understood that this invention canbe embodied in a form other than that described in the foregoing withoutdeparting the spirit of this invention.

What I claim is:

1. In a drying machine including a vertical drying chamber, a guideroller for a strip material to be treated provided at the top of saidchamber, and means for passing the strip material through the interiorof said chamber along an inverted U-shaped path passing over said guideroller, said material within the chamber assuming an inverted U byconfiguration with upwardly and downwardly traveling spans, thecombination therewith of at least two vertically spaced sets of aircurtain creating means positioned below said roller and above the topend of said drying chamber, each of said air curtain creating meansincluding air ejector nozzle means so arranged that the lit) upwardlyand downwardly traveling spans of the material are passed between thenozzles, which direct air toward both surfaces of each span to createair curtains for preventing ascent of hot fluid in the drying chamberalong the spans of the material to said guide roller, the space betweensaid sets of air curtain creating means serving to exhaust the airejected from the nozzle of both sets.

2. The combination as claimed in claim 1, wherein a space is providedbelow the lower set of air curtain creating means and serves to exhaustthe air ejected from the nozzles of the lower set.

3. The combination as claimed in claim 1, wherein said space between thevertically spaced sets of air curtain creating means is connected to aconduit having therein a control valve.

4. The combination as claimed in claim 2, wherein said space below thelower set of air curtain creating means is connected to a conduit havinga control valve.

5. The combination as claimed in claim 2, wherein exhaust fluid fromsaid space between the sets of air curtain creating means is suppliedinto the space below the lower set of air curtain creating means.

6. The combination as claimed in claim 1, wherein said sets of aircurtain creating means and said guide roller are assembled in a topassembly.

7. The combination as claimed in claim 6, wherein said top assembly hasa removable cap.

8. The combination as claimed in claim 6, wherein said top assemblycontains an additional air ejecting device.

9. The combination as claimed in claim 1, wh rein the vertical dryingchamber is divided into a pair of subchambers by a vertical partitionwhich permits communication between the sub-chambers at their upperends, and material heating means are arranged in the chamber along thepath of the material to be dried, and wherein the material is passedthrough a bath of a treating medium dissolved in a solvent before it isintroduced into the drying chamber and solvent recovery means areconnected to the drying chamber for condensing and recovering theevaporated solvent in said chamber.

References Cited UNITED STATES PATENTS 2,532,471 12/1950 Welder 685.42,621,504 12/1952 Spooner 685.4 3,222,895 12/1965 Sheppard 685.43,396,415 8/1968 Windhorst 34-l55 LLOYD L. KING, Primary Examiner

